Clostridium difficile (C. difficile) is the most common known cause of nosocomial diarrhea and accounts for about 3 million cases of diarrhea annually in the United Sates. The risk factors of C. difficile infection (CDI) include exposure to antibiotics, advanced age, and residence in hospitals or long-term care facilities. The symptoms of CDI range from mild diarrhea to pseudomembranous colitis and toxic megacolon. The average cost of treatment is about $10,000 per case. The mortality rate of CDI increased from 5.7 deaths per million population in 1999 to 23.7 deaths per million population in 2004 due to the emergence of hypervirulent outbreak strains. The ribotype 027 strain contributed significantly to the increased CDI incidence. The accurate differentiation of the outbreak strain ribotype 027 from other strains of C. difficile can facilitate decision making for treatment options.